Hi,
For multiple files, you can use OnPreRender event :
int _filecount=0;
void Uploader_FileUploaded(object sender, UploaderEventArgs args)
{
//process the file..
_filecount++;
}
void OnPreRender(EventArgs e)
{
base.OnPreRender(e);
if(_filecount>0)Response.Redirect("thanks.aspx");
}